Some unsteady aerodynamics relevant to insect-inspired flapping-wing micro air vehicles
Flapping-wing micro air vehicles, based on insect-like apping, could potentially
ll a niche in the current market by o ering the ability to gather information from
within buildings. The aerodynamics of insect-like apping are dominated by a
large, lift-enhancing leading-edge vortex (LEV). Historically, the cause and structure
of this vortex have been the subject of controversy. This thesis is primarily
intended to provide insight into the LEV, using computational uid dynamics coupled
with validating experiments. The problem is simpli ed by breaking down the
complex kinematics involved in insect-like apping and examining only a part of
these kinematics; rstly in 2D, before progressing to 3D sweeping wing motions.
The thesis includes discussion of published literature in the eld, highlighting gaps
and inconsistencies in the current knowledge. Among the contributions of this thesis
are: descriptions of the e ects of changing Reynolds number and angle of attack
for 2D and 3D ows; clari cation of terminology and phenomenology, particular in
the context of 2D ows; and detailed descriptions of the development and structure
of the LEV in both 2D and 3D cases, including discussion of Kelvin-Helmholtz instability.
The issues of Strouhal number, delayed leading-edge separation, dynamic
stall and the Wagner e ect are also considered. Generally, the LEV is shown to
be unstable in 2D cases. However, in 3D cases the LEV is seen to be stable, even
if Reynolds number is increased. The stability of the LEV is found to be critically dependent on wing aspect ratio.
Advisor:Knowles, Professor K.
School Location:United Kingdom
Source Type:Master's Thesis
Date of Publication:08/13/2008